When to set a code for a bad IAC?
Then there’s probably a problem with the IAC, a vacuum leak, or a problem with the IAC control circuit. In most cases, cars built after 1996 with onboard diagnostics (OBD) II will set a code for a bad IAC. Many older cars with OBD I will also set a DTC when there’s a problem with the IAC.
Can a bad IAC cause an idle speed to go too high?
As you probably guessed, a faulty IAC can result in an idle speed that’s either too high or too low, depending on whether the device is stuck open or stuck closed. An idle speed that bounces up and down is also a possibility.
How to test an idle air control valve?
How to Test an Idle Air Control Valve 1 Check for Diagnostic Trouble Codes (DTCs) Is there an idle speed or other IAC-related DTC stored? 2 Perform a Visual Inspection If you find IAC or idle speed codes stored, you can move on to performing a visual inspection. 3 Test the IAC Valve (Without an OEM-Level Scan Tool)
How can you check the resistance of an IAC?
One way you can check an IAC is by measuring its electrical resistance. Keep in mind, however, that this test is not conclusive. You’re only testing the electrical portion of the IAC, not the mechanical part. To check resistance, you will need a repair manual and a digital multimeter (DMM).
What happens when the idle air control valve ( IAC ) fails?
When the idle air control valve (IAC) fails it can cause all sorts of issues; and in some cases may even render it undrivable. Usually, a bad or failing idle air control valve (IAC); will produce a few symptoms that can alert the driver of a potential issue:
Can a bad IAC cause a DTC to set?
If you do not hear a change in RPMs, do not assume the IAC is bad until you do further testing. Also, this test may cause DTCs to set. With the engine off, unplug the IAC. Then start the engine and listen for an idle speed that’s either too high, too low, or fluctuating.
Can a bad IAC valve cause a surging condition?
A bad IAC valve can also cause a surging condition at idle, where the RPMs will increase and then drop back to normal. 2. Your check engine light is on: The computer monitors the IAC valve to make sure it’s working correctly.
How to test the coil driver circuits in the IAC valve?
How To test the coil driver circuits in the (IAC) valve: Using an ohmmeter, measure the resistance between pins 3 and 2 on the (IAC) valve. Resistance should be 10-14 ohms. If resistance is ok, proceed to the next step.